Over the past few years, there has been tremendous interest in exploiting nanotechnology materials and devices in the diagnostic and/or treatment of biological problems or diseases, including the treatment of infections and/or human cellular diseases. However, so far the interactions between carbon nanomaterials and cellular physiology have been characterized as an issue of biochemical mechanisms involving molecular transport, cellular adhesion, etc.
Ultrasound imaging is a widely applied technique in clinical research and treatment, where sound waves are projected towards an object and the reflected waves are analysed. Ultrasound imaging, however, has some major drawbacks. Achieving high axial and spatial resolution comes at the price of penetration depth. Frequencies of 30 to 55 MHz are typically used, providing an image which is highly resolved, but shallow. For deep structures, lower frequencies in the range of 1-18 MHz are applied, enabling a greater penetration depth, but with a limited image resolution in either axis. Several strategies have been developed to resolve this issue, such as image reconstruction techniques to lower background noise, the creation of synthetic apertures, and, finally, by contrast-enhanced ultrasound approaches.
Contrast-enhanced ultrasound (CEUS) is a technique where contrast agents having ligands allowing them to bind to the cells of interest are injected in the patient. The technique is however limited to entities that can cause an intense reflection or generate significant echogenicity, i.e., the ability to reflect sound waves. Currently, the major and only commercial contrast agents are microbubbles, which are filled with a gas, usually using perfluorcarbons. The microbubbles oscillate in the presence of the ultrasonic field, generating the backscatter that can be detected with a strong contrast to surrounding tissues. One drawback of microbubbles is the use of perfluorocarbons, which last but a few short minutes in the blood and are highly expensive, prohibiting their widespread use. The presence of microbubbles is also detrimental to patient health, resulting in head pains, nausea and other side effects of use in a significant number of patients, which provides an incentive to avoid their use from a clinical prospective.
Nanofluids comprising nanoparticles dispersed in a fluid where the physical material is defined as nano and is dispersed. Nanoparticles such as carbon nanotubes (CNT), carbon nanoparticles and hybrid particle systems can be modified by physical or chemical processes to enhance their dispersibility in the fluid. However, these nanofluids are not suitable to enable or elicit bio-specific biological responses. Nanofluids that are not biomodified, are not able of delivering specific targeted effects. Bionanofluid definitions require the inclusion of bio-related or bio-molecular functionalization that is specific to a desired application.